Growing Degree Accumulation and Rainfall Through June 22nd

Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu; Cory Whaley, Sussex Co. Extension Ag Agent, whaley@udel.edu; James Adkins, Irrigation Engineer, adkins@udel.edu, Jake Jones, Extension Agriculture Agent, Kent County, jgjones@udel.edu, Dan Severson, Agriculture Agent, New Castle County, severson@udel.edu

Corn planted around late April in Sussex County is at the V8/9 stage, later plantings right behind it. Fields planted in the second half of May should be at or close to V6 in most parts of the state (Table 1), and you should start planning for sidedress applications. The weather has continued to be unpredictable in June, particularly in regards to temperature, but we have seen a steady linear accumulation of GDD compared to May (Figure 1). We are averaging about 21 GDD per day, and if you planted in mid April, we would expect to see the start of tasseling the July 4^th weekend and R1 in mid-July (Figure 1).

Table 1: Accumulated growing degree-days based on planting dates through June 22^nd.

V12 = 870 GDD, VT = 1135 GDD, R1 = 1400 GDD

We have received between 7-9 inches (Figure 2) across the state since April 15^th, with our driest stretch at the beginning of May. Many large rainfall events have occurred, dropping between 1-3 inches. Depending on soil type and infiltration rate, these high rainfall events may runoff, and not always move into the soil profile. The graph in Figure 2 only represents one weather station in each county and is not a county average. Sussex County has a lot of very dry areas, where some parts of the county have received less than one inch over the last month. Anyone with irrigation should be checking field moisture and keeping up with timely additions.

Figure 1. Growing degree day accumulation since April 15^th.

Figure 2. Statewide rainfall accumulation since April 15^th.